The present invention relates to automatic dishwashing machines (dishwashers) and in particular to a dishwasher vent for use in a low noise dishwasher.
Dishwashers, such as those found in many homes, provide a chamber holding one or more racks into which eating utensils and cookware may be placed for cleaning. The chamber may be closed by a door opening at the front of the chamber to allow loading and unloading of the chamber.
The door is closed during a washing cycle to prevent the escape of water sprayed within the volume of the chamber to wash items placed in the rack. Upon completion of the washing cycle, a drying cycle is initiated during which water is drained from the chamber and moist air is discharged through a vent. Cool air pulled into the chamber through a lower vent rapidly dries the heated dishes.
Dishwashers can be loud, particularly during the washing cycle, with noise coming from the agitated water, movement of the dishes, and the dishwasher mechanism of pump and motor. Some of this noise can be reduced by properly shrouding the washing chamber with acoustically absorbent material, nevertheless, even with a properly shrouded chamber, a substantial amount of noise can escape through the vent by diffraction.
One method of reducing vent-transmitted noise is by offsetting the inlet and outlet of the vent to provide a baffling that prevents direct passage of sound through the vent opening. This approach can also prevent water from passing through the vent.
A second method of reducing vent-transmitted noise is to close the vent with a valve plate or similar mechanism during the washing cycle and open the vent only during the drying cycle. A vent suitable for this purpose is described in U.S. Pat. No. 6,293,289 filed Nov. 8, 1999, assigned to the assignee of the present invention, and hereby incorporated by reference. This patent describes, in one embodiment, a wax motor operating a hinged valve plate that opens and closes to control air and sound flow through the vent. The hinged plate may also be independently opened by excess pressure in the washing machine so as to accommodate “surge pressures” resulting, for example, from pressure build up caused by an opening and closing of the dishwasher in mid-cycle where introduced cold air is rapidly heated by dishes and hot water when the door is resealed.
Superior drying requires that the vent area be made as large as possible when the vent is open and that the valve plate provide minimal obstruction to the flowing air. This may be done by placing the hinge axis of the valve plate generally parallel to the front and rear surfaces so that the valve plate opens to align with the natural flow lines of air.
The actuator for a valve plate in a vent may be positioned outside of the vent housing (defining the vent passage) to improve airflow and to protect the actuator from water. This may be accomplished by extending the shaft about which the vent plate rotates out of the vent housing through a journal hole in one wall of the vent to be engaged by an actuator. The journal hole is kept small to prevent the escape of water from the vent and may include a seal.
Mechanically, passing the shaft through a wall of the vent housing requires either that the vent plate be detachable from the shaft, so that the shaft may be inserted through a journal hole into the housing without obstruction, or that the housing be separable into two halves to allow an integral vent plate/shaft assembly to be positioned in the vent body and the housing closed over that. Both of these approaches increase the complexity of manufacturing the vent: the former requiring assembly of the shaft and vent plate from inside of the vent, and the latter requiring assembly of the vent housing from several pieces.